This invention relates generally to biocides and, more particularly, to compositions containing hops extract and their use in water systems and process streams to control biological fouling.
Growth of microorganisms such as bacteria, fungi and algae, as well as macroorganisms such as mussels and clams, is problematic in water systems and process streams. As used herein, xe2x80x9cwater systemsxe2x80x9d is defined to include municipal, commercial and industrial water systems, as well as aqueous streams. The term xe2x80x9caqueous streamsxe2x80x9d includes, but is not limited to, streams used for transporting or processing food products and on food surfaces and equipment surfaces that come in contact with the aqueous stream. Examples of food products include fruits vegetables and tubers such as tomatoes, potatoes, bananas, apples, beets, and the like, and meats such as poultry, beef and the like and the surfaces thereof. xe2x80x9cProcess streams,xe2x80x9d as used herein includes, but is not limited to, sugar beet diffuser systems.
Proliferation of microorganisms and macroorganisms can cause mechanical, operational and chemical problems with economic and health-related consequences. Similarly, growth of microorganisms in aqueous streams is undesirable. Poor biological control in these systems can cause product spoilage and loss, high water use rates, and the potential for health-related problems.
Many of the chemicals used to control biological fouling in water systems and process streams were developed based on efficacy, without primary emphasis on safety and environmental compatibility. Many of these chemicals are toxic to terrestrial animals or aquatic life, are eye or skin irritants, can produce sensitization reactions with repeated exposure, or have toxic byproducts. There are many naturally-occurring substances with biocidal properties. Natural substances that control microbial fouling have been, to some extent, optimized through evolution and are, by definition, environmentally compatible. Product research and development guided by the use or imitation of natural microbial fouling control substances has the potential to provide useful and innovative water treatment chemistries.
Hops extract is typically produced as an amber colored liquid used primarily for flavor enhancement of beer. Hops extract is obtained from the hop plant (Humulus lupulus) as a group of resins, commonly referred to as alpha acids, represented by humulone and its congeners (cohumulone, adhumulone) and beta acids, represented by lupulone and its congeners (colupulone, adlupulone). Beta acid (lupulone) extracts from hops are a product of the brewing process. Hops beta acid extracts are also produced for use in the brewing process to alter properties of the finished beverage. Therefore, abundant sources of raw material for hops extract-based biological control products are available. The fact that hops extract alpha and beta acids are routinely consumed by humans emphasizes the favorable toxicity profile of these substances.
As known in the brewing industry, some hop acids have antimicrobial activity against specific bacteria. For example, U.S. Pat. Nos. 5,082,975 and 5,166,449 disclose that the hop acid hexahydrolupulone inhibits the growth of certain Lactobacillus species. Similarly, U.S. Pat. No. 5,455,038 discloses the use of tetrahydroisohumulone or hexahydrocolupulone to inhibit the growth of Listeria species in food and food packaging materials; U.S. Pat. No. 5,370,863 discloses the use of specific alpha and beta hop acids in oral care compositions for inhibition of microorganisms that cause plaque and periodontal disease; and U.S. Pat. No. 5,286,506 discloses the use of hops extract beta acids to control pathogenic bacteria, such as Listeria, in food.
In general, hops extract is a bacterial inhibitor, not a bactericidal agent. Hops extract has poor efficacy against Gram-negative bacteria which are major slime-producing organisms in many water systems. Hops extract is more effective against Gram-positive bacteria. For example, Leuconostoc mesenteroides is a significant problematic microorganism in sugar beet processing and diffuser systems and is a Gram-positive organism which is susceptible to hops extract. Glutaraldehyde and other biocides are currently used in sugar beet diffusion systems to control microbiological fouling due to Leuconostoc and other bacteria. However, none of the biocides currently used in this application, including glutaraldehyde, are as safe as hops extract. The use of hops extract in the sugar industry for microbial control has been previously disclosed (Pollach, et al., Zuckerind. 121 (1996) Nr. 12, S. 919-926; Hein et al., Zuckerind. 122 (1997) Nr. 12, S. 940-949; and Pollach et al., Zuckerind. 124 (1999) Nr. 8, S. 622-637).
Growth of algae can be a problem in any water system exposed to sunlight. Uncontrolled algae growth typically begins as a cosmetic problem, but can lead to problems such as distribution deck plugging and increased halogen demand in cooling towers, and unacceptable water quality in swimming pools, decorative fountain and other water features. Although there are numerous non-oxidizing biocides available for algae control, many of these biocides have high human and environmental toxicity.
Chemistries found naturally or which mimic natural chemical processes are commonly referred to as xe2x80x9cgreen.xe2x80x9d As environmental restrictions and regulations governing biocides increase, use of some biocides may be restricted. Therefore, green biocides such hops extract may provide an effective and environmentally sound biocide alternative in water treatment.
Accordingly, it would be desirable to provide a method of controlling biological fouling in water systems and process streams using hops extract, a naturally-occurring biological control agent, which is safe and environmentally compatible.
It would also be desirable to provide novel biocidal compositions containing hops extract, in combination with other biocides.
It would furthermore be desirable to provide novel biocidal compositions containing hops extract stabilized with surfactants to prevent hops extract product degradation, separation and precipitate formation prior to application. This surfactant-stabilized hops extract may contain hops extract alone or in combination with other biocides.
The present invention calls for adding hops extract to a water system or process stream to control biological fouling. Hops extract can be applied with greater safety, convenience and lower environmental impact than currently available biocides.
The present invention is directed to a composition and method of controlling biological fouling in water systems and process streams. In accordance with this invention, hops extract is added to the water system or process stream.
As used herein, xe2x80x9chops extractxe2x80x9d is defined as extracts which are primarily composed of beta acids, but which may also contain alpha acids. xe2x80x9cBeta acidsxe2x80x9d are defined as lupulone, colupulone, adlupulone, hydrogenated lupulone, hydrogenated colupulone, hydrogenated adlupulone, mixtures thereof and the salts thereof. xe2x80x9cAlpha acidsxe2x80x9d are defined as humulone, cohumulone, adhumulone, hydrogenated humulone, hydrogenated cohumulone, hydrogenated adhumulone, and the isomerized (cis- and trans-) alpha acids, their congeners and their hydrogenated forms, mixtures thereof and the salts thereof.
The biological growth controlled by the method of the present invention may be microbiological or macrobiological in nature. As used herein, xe2x80x9ccontrolxe2x80x9d is defined to include inhibition, killing and removal. Microbiological growth includes bacteria, fungi, algae and combinations thereof. Macrobiological growth includes, but is not limited to, zebra mussels, blue mussels and the Asiatic clam.
The water systems to which hops extract may be added to control biological fouling include potable waters, cooling waters; food, beverage, and industrial process waters; pulp and paper mill systems; brewery pasteurizers; sweetwater systems; air washer systems; oil field drilling fluids and muds; petroleum recovery processes; industrial lubricants; cutting fluids; heat transfer systems; gas scrubber systems; latex systems; clay and pigment systems; decorative fountains; water intake pipes; ballast water tanks; and ship reservoirs, among others.
The hops extract is added to the water system or process stream by any conventional method at a concentration which effectively controls biological fouling. It is preferred that the amount of hops extract be in the range of about 0.01 ppm to about 10,000 ppm. More preferably, the amount of hops extract is from about 0.05 ppm to about 50 ppm, with about 0.1 to about 10 ppm being most preferred.
Prior to its addition to the water system or process stream, the hops extract may optionally be stabilized with one or more surfactants such as dioctyl sodium sulfosuccinate, sodium mono- and dimethyl naphthalene sulfonates, N-lauroyl sarcosine sodium salt, alkyl polyglycoside and sodium dodecyl diphenyloxide disulfonate. Other surfactant chemistries may also be used and are expected to similarly stabilize hops extracts. Some surfactants that are obvious choices for use in stabilizing hops extract are those surfactants approved by regulatory agencies for indirect or direct food contact or for direct addition to food.
These surfactant and hops extract compositions are intended to illustrate the general invention that hops extracts can be stabilized by adding surfactants. This stabilization inhibits or prevents precipitate formation in the extract and preserves the integrity of the product prior to addition to the water system or process stream. Stabilization of hops extract by use of this invention makes use of hops extract for biological control possible in applications where large hops extract product volumes are required and where hops extract exposed to ambient environmental conditions is stored or used for biological control over extended periods of time.
One or more biocides may be added to the water system or process stream along with the hops extract to control biological fouling. Examples of suitable biocides include 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, glutaraldehyde, 2,2-dibromo-3-nitrilopropionamide, 2-bromo-2-nitropropane-1,3 diol, 1-bromo-1-(bromomethyl)-1,3-propanedicarbonitrile, tetrachloroisophthalonitrile, alkyldimethylbenzylammonium chloride, dimethyl dialkyl ammonium chloride, poly(oxyethylene(dimethyliminio)ethylene(diemethyliminio)ethylene dichloride, methylene bisthiocyanate, 2-decylthioethanamine, tetrakishydroxymethyl phosphonium sulfate, dithiocarbamate, cyanodithioimidocarbonate, 2-methyl-5-nitroimidazole-1-ethanol, 2-(2-bromo-2-nitroethenyl)furan, beta-bromo-beta-nitrostyrene, beta-nitrostyrene, beta-nitrovinyl furan, 2-bromo-2-bromomethyl glutaronitrile, bis(trichloromethyl)sulfone, S-(2-hydroxypropyl)thiomethanesulfonate, tetrahydro-3,5-dimethyl-2H-1,3,5-hydrazine-2-thione, 2-(thiocyanomethylthio)benzothiazole, 2-bromo-4xe2x80x2-hydroxyacetophenone, 1,4-bis(bromoacetoxy)-2-butene, bis(tributyltin)oxide, copper sulfate, (2-tert-butylamino)-4-chloro-6-(ethylamino)-s-triazine, dodecylguanidine acetate, dodecylguanidine hydrochloride, coco alkyldimethylamine oxide, n-coco alkyltrimethylenediamine, tetra-alkyl phosphonium chloride, 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid, 2-(4-thiazolyl)-benzimidazole, orthophenylphenol, 6-ethoxy-1,2-dihydro-2,2,4-trimethyl quinoline and 4,5-dichloro-2-n-octyl-4-isothiazoline-3-one.
The biocides may be added to the water system or process stream by any conventional method. It is preferred that the amount of biocide be in the range of about 0.01 ppm to about 10,000 ppm. More preferably, the amount of biocide is from about 0.05 ppm to about 50 ppm, with about 0.1 ppm to about 10 ppm being most preferred.
The use of hops extract and another biocide in combination surprisingly leads to unexpectedly superior results and allows for significantly less use when utilized in combination, as compared to the amount of each needed individually to achieve the same biocidal performance. This biocidal synergy of the combined hops extract and biocide can be achieved by adding hops extract and a biocide to the water system or process stream simultaneously from individual containers or by applying a single composition that contains both hops extract and biocide.
The present invention provides superior biological fouling control when a composition is added to the water system, or process stream which contains hops extract and at least one biocide selected from the group consisting of 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, glutaraldehyde, 2,2-dibromo-3-nitrilopropionamide, 2-bromo-2-nitropropane-1,3 diol, 1-bromo-1-(bromomethyl)-1,3-propanedicarbonitrile, tetrachloroisophthalonitrile, alkyldimethylbenzylammonium chloride, dimethyl dialkyl ammonium chloride, poly(oxyethylene(dimethyliminio)ethylene(diemethyliminio)ethylene dichloride, methylene bisthiocyanate, 2-decylthioethanamine, tetrakishydroxymethyl phosphonium sulfate, dithiocarbamate, cyanodithioimidocarbonate, 2-methyl-5-nitroimidazole-1-ethanol, 2-(2-bromo-2-nitroethenyl)furan, beta-bromo-beta-nitrostyrene, beta-nitrostyrene, beta-nitrovinyl furan, 2-bromo-2-bromomethyl glutaronitrile, bis(trichloromethyl)sulfone, S-(2-hydroxypropyl)thiomethanesulfonate, tetrahydro-3,5-dimethyl-2H-1,3,5-hydrazine-2-thione, 2-(thiocyanomethylthio)benzothiazole, 2-bromo-4xe2x80x2-hydroxyacetophenone, 1,4-bis(bromoacetoxy)-2-butene, bis(tributyltin)oxide, copper sulfate, (2-tert-butylamino)-4-chloro-6-(ethylamino)-s-triazine, dodecylguanidine acetate, dodecylguanidine hydrochloride, coco alkyldimethylamine oxide, n-coco alkyltrimethylenediamine, tetra-alkyl phosphonium chloride, 7-oxabicyclo [2.2.1]heptane-2,3-dicarboxylic acid, 2-(4-thiazolyl)-benzimidazole, orthophenylphenol, 6-ethoxy-1,2-dihydro-2,2,4-trimethyl quinoline and 4,5-dichloro-2-n-octyl-4-isothiazoline-3-one.
It is preferred that the amount of hops extract in the composition be in the range of about 0.1% to about 99% and the amount of biocide be in the range of about 0.1% to about 99%.
The hops extract in the synergistic hops extract/biocide composition may also be stabilized with one or more surfactants to prevent the precipitation of the beta acids over time. Suitable surfactants include, but are not limited to, dioctyl sodium sulfosuccinate, sodium mono- and dimethyl naphthalene sulfonates, N-lauroyl sarcosine sodium salt, alkyl polyglycoside and sodium dodecyl diphenyloxide disulfonate. Other surfactant chemistries may also be used and are expected to similarly stabilize hops extracts. Some surfactants that are obvious choices for use in stabilizing hops extract are those surfactants approved by regulatory agencies for indirect or direct food contact or for direct addition to food.
It is preferred that the amount of hops extract in the composition be in the range of about 0.1% to about 99%, the amount of biocide be in the range of about 0.1% to about 99% and the amount of surfactant be in the range of about 0.1% to about 99%.
The present inventors have surprisingly discovered that biological fouling can be effectively controlled in water systems and process streams through the addition of hops extract. In addition, hops extract can be applied with greater safety, convenience and lower environmental impact than currently available biocides. Moreover, the present invention improves on current technology by demonstrating synergy between hops extract and a wide variety of other biocides. Hops extract and biocides may be used in synergistic combinations to yield better biocidal performance than when hops extract or the biocides are used individually. Hops extract and each biocide may act on target organisms in different ways to cause cell growth inhibition or death. In addition, using a combination of hops extract and one or more biocides allows for application of less total hops extract and/or biocide to achieve a desired level of control. This has safety, environmental and economic advantages. It allows for reduced discharge of potential pollutants, safer application and a more cost effective biological control program.
Safety, as well as low human and environmental toxicities, are some of the primary advantages of the inventive compositions compared to previously described compositions used to control biological fouling. In addition to these primary advantages, the inventive compositions have other benefits such as low volatility and lack of malodors.
Furthermore, this invention provides algicidal and algistatic activities of hops extracts alone and in synergistic compositions with other biocides. The activity of hops extract against algae has not been described previously and was surprising. These compositions are potentially useful in controlling algae in a wide variety of water systems exposed to sunlight and in controlling other organisms that grow in water systems and process streams.